U.S. Pat. Nos. 4,203,445 and 4,274,848 disclose ostomy pouches in which deodorizing gas filters are mounted. The wall portions of the pouches that overlie the filters are dome-shaped and provided with S-shaped slits for venting gases from the pouches. The slits serve as normally-closed flap valves with the flaps flexing outwardly into open positions when gas pressure within the pouches exceeds ambient pressure.
While the S-shaped flap vent of such a pouch assumes a closed condition in the absence of a pressure differential or other force, it is possible that the flap (or flaps) might also flex inwardly to allow liquid to enter a pouch when, for example, such a pouch is worn by an ostomate while taking a shower. Although only a small amount of water would be expected to pass inwardly through such vent opening, the volume necessary to cause an adverse effect on filter operation would also be small.
The present invention addresses this concern by providing a construction in which a filter assembly is provided with a second flap vent behind, but preferably out of register with, the flap vent of the pouch. More specifically, the filter assembly comprises a planar deodorizing gas filter enclosed in a flat envelope composed of an inner panel of gas-permeable but liquid-impervious sheet material and an outer panel of gas- and liquid-impervious sheet material. The outer panel has its peripheral portion sealed to the wall of the pouch along a continuous seal line spaced from and extending about the flap vent of the pouch. A flat vent chamber is thereby formed (or develops in use) between the pouch wall and the central portion-of the filter assembly's outer panel. It is the panel's central portion that is provided with a second flap vent in the form of a curvilinear slit defining at least one flap that normally assumes a closed position coplanar with the panel's central portion but that is capable of flexing outwardly into an open position to vent gases from the pouch when the pressure therein exceeds ambient pressure. Filtered gases entering the vent chamber may then pass outwardly from that chamber through the flap vent in the pouch wall.
The second flap vent--the one provided by the filter assembly--also performs a security function in protecting the filter against liquid contact. Thus, in the shower, a small amount of water might enter the vent chamber should a spray of water impinge on the flap or flaps of the pouch vent, since such flaps are free to flex inwardly as well as outwardly. In contrast, the flap or flaps of the vent in the central portion of the filter assembly's outer panel tend to remain closed, partly because they are shielded by the pouch wall against direct contact by such a spray and partly because they are braced by the planar gas filter disposed directly therebehind. Unlike the flaps of the pouch vent, the flaps of the filter vent, although free to flex outwardly into open positions in the vent chamber in response to increasing gas pressure within the pouch, are restrained against inward flexure by the remainder of the filter assembly located within the pouch. Because of the relationship of parts, the flap vent of the filter assembly essentially functions as a one-way valve, in contrast to the flap vent of the pouch wall which allows flow in either direction.
The flap vents of the pouch and filter assembly preferably assume the configuration of S-shaped slits, each slit thereby defining two flaps. While the flap vents are necessarily in close proximity because of the relatively small size of the filter assembly, it is desirable that they not be in register with each other. Most advantageously, two flap vents are not only out of register but are laterally displaced so that the flaps of one vent cannot interfere with or directly affect the operation of the flaps of the other vent.
Other features, advantages, and objects will become apparent from the specification and drawings.